1. Field of the Invention
In one aspect, the invention relates to a hinged plate for pivotally attaching a pair of lumber members together in a double-hinged manner. In another aspect, the invention relates to a building truss incorporating the double-hinged plate. In a further aspect, the invention relates to methods for assembling and erecting a truss incorporating a foldable portion for easy transport.
2. Description of the Related Art
Residential and manufactured homes, as with any building or dwelling, comprise a skeletal structure typically including a floor which supports one or more walls upon which a ceiling and roof are mounted. The ceiling and roof are typically formed by a roof truss, generally formed in a triangular shape which forms, at its lower surface, a ceiling for the interior of the structure and, at its upper surface, a roof for the exterior of the structure.
A typical factory-built structure is shown generally by reference numeral 10 in FIG. 1 comprising a floor structure 12 supporting a plurality of walls 14 thereon. A roof truss 16 is mounted atop the walls 14. The roof truss 16 typically comprises a bottom chord 18 mounted to the walls 14. A web 20 and a ridge beam/kingpost 22 typically extend upwardly from the bottom chord at about a middle portion and an inner end portion of the bottom chord 18, respectively. A lower top chord 24 is typically mounted at an outer end to the bottom chord 24 (a portion of which forms an eaves overhang 26) and at an inner end to an upper end of the web 20. A diagonal web 28 typically extends between an upper portion of the web 20 to the inner end of the bottom chord 18 for structural support. A kneewall 30 often extends angularly and upwardly from the top surface of the ridge beam 22 toward (and mounted to) an inner and upper end of an upper top chord 32 which, in turn, is mounted at a lower, outer end by a hinge plate 34 to the upper end of the lower top chord 24. Conventional nail plates 36 typically accomplish many of the fixed connections between the chord members of the roof truss 16.
Factory-built or manufactured homes are usually constructed in modular units, typically in widths of 10 to 18 feet. This allows the factory-built home to be transported from the factory to the building site. Both width and height restrictions create special challenges and have to be resolved before home shipment can take place. There are often competitive pressures on the factory-built housing to incorporate new architectural features comparable to site-built housing. One desirable feature often requested in manufactured homes is a roof having a steep pitch. In order to be able to manufacture a roof system with a steep pitch off-site and to easily transport the home to a building site, many factory-built homes have trusses that allow the top chord to be lowered (such as that shown in FIG. 1 with the pivotally-mounted lower and upper top chords 24 and 32 by the hinge plate 34).
The pivotable top chord is required so that the roof pitch can be temporarily lowered to allow the home to be transported without exceeding over-the-road height limitations of state highway transportation authorities. When the top chord is lowered, the high end extends past the module on steep pitch roofs which creates width problems. Many manufacturers typically leave the upper or peak section of the roof off so that it can be re-assembled into place at the building site. These extra manufacturing and assembly steps cause manufacturing inefficiencies and quality control problems, typically resulting in an increased cost.
Some attempts have been made in the past to address these problems. First, some prior art systems incorporate a “built-up” cap that is fastened to the upper top chord with a variable size steel strap. Second, rather than attaching the built-up cap with a strap, the cap (which forms the peak of the truss) is shipped as a separate component to the truss and is assembled to the truss at the building site. A third solution is shown in U.S. Pat. No. 5,094,059 to Ganescu, issued Mar. 10, 1992, which uses a double-hinge connector plate which, due to the significant unrestrained shear forces encountered by this plate, requires substantial in-factory and/or on-site work to be performed in order to achieve structural soundness of the truss. A reinforcing member is normally required or vertical supports are needed on both sides of the double-hinge plate.
Although past attempts can not be considered total failures, all have serious shortcomings in that they need substantial amounts of reinforcement that normally take place at the building site. As for the first solution mentioned in the previous paragraph, the aforementioned metal strap is easily twisted in transportation, which creates alignment problems upon reaching the building site. The built-up cap also requires substantial assembly at the building site to create a truss with structural integrity. The double-hinge plate of the Ganescu '059 patent is insufficient without additional in-factory and/or on-site structural add-ons to achieve structural integrity.